Extruded honeycomb catalysts are one-piece, monolithic objects, which have a plurality of channels through which the exhaust gas flows during operation. These channels have an opening width of just a few millimeters. The webs delimiting the individual channels also typically have a width of just 300 μm. In extruded honeycomb catalysts, in which the solid material is catalytically active, a high proportion by volume of the solid body consists of catalytically active components. The result of this is that any modifications of the catalytic components, for example to make adaptations to different requirements and in general to pursue refinements, have a critical effect on extrudability. Altogether, this makes the development period for a new extruded honeycomb catalyst, in which the solid material is catalytically active, expensive.
WO 2010/099395 A1 discloses extruded honeycomb catalyst bodies and methods of manufacturing them. The catalyst body includes a first oxide selected from the group consisting of tungsten oxides, vanadium oxides and combinations thereof, a second oxide selected from the group consisting of cerium oxides, lanthanum oxides, zirconium oxides and combinations thereof and a zeolite. In one embodiment, an extruded zeolite core is coated with a layer of a mixture of a cerium oxide, a zirconium oxide and a tungsten oxide.
Thus, there is a need for specifying a honeycomb catalyst which can be adapted to new requirements with low development costs.